Method of managing a system for the manufacture of tobacco products

ABSTRACT

A system for manufacturing tobacco products is managed using a method whereby, having programmed a number (P n ) into a master control unit ( 33 ) that represents a nominal production target for products of a given brand, such as boxes filled with cartons containing cigarettes of the particular brand, and programmed a number (C max ) representing the maximum output capacity of the system, or in practice the maximum quantity of products in process that the system is able to handle, a tally (P) of products is kept, and, at a given moment (t 1 ) following the completion of a number (P r ) of products that matches the target (P n =P r +C max ), a first check is run on the quantity (C 1 ) of the product actually turned out by the system; should it emerge from this first flash check that the actual quantity (C 1 ) is equal to the maximum output capacity (C max ), then a brand changeover procedure will be initiated by the master control unit ( 33 ), whereas if the actual quantity (C 1 ) produced is less than the maximum output capacity (C max ), further flash checks will be run at intervals established by events dependent on the measured output, and repeated until the sum of the number (P) of single products counted plus the actual quantity (C) turned out is equal to the nominal production target (P n ).

TECHNICAL FIELD

The present invention relates to a method of managing a system for themanufacture of tobacco products.

BACKGROUND ART

Systems for manufacturing tobacco products will generally comprise aplurality of machines linked one to another along a common productionline. In particular, such machines will include a cigarette maker at theupstream end of the line and, arranged in succession proceeding towardthe downstream end, a filter tip attachment, a packer, a cellophaner, acartoner and finally a machine by which pluralities of cartons areparcelled into boxes of whatever type, ready for despatch. Where largeboxes are used, the despatch area will be equipped with an end-of-linepalletizer.

The system may also comprise a filter plug maker associated with thefilter tip attachment, and a number of inline storage units locatedbetween the single machines of the system, serving to compensate anydifferences in operating speed between one machine and the next.

In manufacturing systems of the type in question, each machine needs tobe re-supplied periodically with consumables and packaging materials,including tobacco filler, filter plugs, rolls of cigarette paper, metalfoil paper and thermoplastic material, packet blanks, coupons, revenuestamps, and so forth. To this end, each machine is equipped with atleast one sensor monitoring the depletion of the relative materials, aswell as a counter positioned at the outfeed stage of the machine andserving to indicate the number of items turned out.

The demands of the market at the present time are such that individualbrands tend to be manufactured in short runs. This means that there arefrequent changeover operations, which impact negatively on the long-termproductivity of manufacturing systems. With each changeover, in effect,the machines have to be shut down and emptied, and the variousconsumables replaced entirely or in part.

Conventionally, the task of renewing the supply of consumables to thevarious machines is carried out by production line operators, relying onan approximate and empirical approach and allowing generous margins ofsafety so as to ensure the scheduled production target can be reachedcomfortably, in readiness for changeover to another brand. This resultsin a measure of overproduction, compared to the original target, and/orthe waste of a notable quantity of consumable materials alreadyoccupying the production line of the system, which cannot be used in thesubsequent run to manufacture tobacco products of a different brand. Theoperation of removing large quantities of material from the productionline and returning these same materials to stock possibly for subsequentuse is one that requires a relatively long period of time to complete,and, besides the negative impact on the productivity of the system asalready intimated, there is also the risk that the materials could bedamaged during handling and transit.

The object of the present invention is to provide a method of managing asystem for the manufacture of tobacco products, such as will beunaffected by the drawbacks mentioned above and, more particularly,effective in minimizing the waste of consumables, avoiding damage toconsumable materials and limiting overproduction in respect of scheduledtargets.

A further object of the invention is to provide a method of managing asystem for the manufacture of tobacco products that will be easilyimplemented and can be run automatically by a monitoring, processing andcontrol system using a limited number of sensing and computingoperations.

DISCLOSURE OF THE INVENTION

The stated objects are realized in a method according to the presentinvention, of which the characterizing features are readily discerniblefrom the content of claim 1 appended and preferably from any one of theclaims directly or independently dependent on claim 1.

The invention will now be described in detail, by way of example, withthe aid of the accompanying drawings, in which:

FIG. 1 shows a schematic illustration of a system for the manufacture oftobacco products allowing implementation of the method according to thepresent invention;

FIG. 2 is a block diagram showing a first preferred procedure forimplementation of the method of managing and controlling the systemillustrated in FIG. 1;

figure is a block diagram showing a second procedure for implementationof the method of managing and controlling the system illustrated in FIG.1.

Referring to FIG. 1 of the drawings, 1 denotes a system for themanufacture and packaging of tobacco products, in its entirety,comprising a plurality of machines linked one to another along aproduction line denoted 2. More exactly, and proceeding from theupstream to the downstream end of the line 2 along the flow path, thesystem 1 incorporates a cigarette maker 3 turning out cigarette sticks4, a filter tip attachment 5 turning out filter cigarettes 6, and apacker 5 turning out packets 9 of cigarettes. The packer 7 is connectedon the one hand to the filter tip attachment 5, by way of a buffer 8allowing temporary inline storage of the filter cigarettes 6, and on theother to a cellophaner 10 turning out overwrapped packets 11. Theoverwrapped packets 11 emerging from the cellophaner 10 are directedinto a cartoner 12 by which the selfsame packets 11 are packaged incartons 13. The cartons are then conveyed into a parceller 14, by whichthey are packed into boxes 15 of whatever size and style and 9 directedtoward an outfeed station of the line 2.

The various machines 3, 5, 7, 10, 12 and 14 are interconnected along theline 2 by means of conveyor devices, of which the conveyor 16 linkingthe filter tip attachment 5 and the packer 7 and the conveyor 17 linkingthe packer 7 and the cellophaner 10, in particular, are indicated inFIG. 1.

The line 2 is supplied at points alongside each of the machines 3, 5, 7,10, 12 and 14 with respective wrapping materials, all denoted 18 andconsisting in rolls of paper, metal foil and polypropylene, cardboardblanks and the like. Also supplied to the line 2 are additional and/orauxiliary materials such as coupons and revenue stamps, denoted 19generically in FIG. 1.

Associated with each of the machines 3, 5, 7, 10, 12 and 14, andindicated by relative blocks, are respective counters such as willgenerate a signal indicating the number of products turned out by eachmachine 3, 5, 7, 10, 12 and 14. In particular, two counters denoted 20and 21 are associated with the machines 3 and 5 producing the cigarettesticks 4 and filter cigarettes 6, respectively; two counters 22 and 23are associated respectively with the packer 7 and the cellophaner 10,serving to keep a tally of erected packets 9 and overwrapped packets 11;and two further counters 24 and 25 associated with the cartoner 12 andthe parceller 14 serve respectively to keep a tally of the cartons 13and of the filled boxes 15 at the aforementioned outfeed station.

Also forming part of the system, and illustrated by relative blocks, aresensors able to generate a signal indicating the consumption of thewrapping materials 18 and the additional and/or auxiliary materials 19utilized by the corresponding machine during its operation. Inparticular, sensors 26 and 27 associated respectively with the cigarettemaker 3 and with the filter tip attachment 5 serve to monitor theconsumption of the rolls 18 of paper material used to make the cigarettesticks 4 and the filter cigarettes 6, respectively; similarly, sensors28, 29, 30 and 31 associated with the packer 7, the cellophaner 10, thecartoner 12 and the parceller 14 serve to monitor the consumption of thematerials 18 used by these same machines, typically rolls,,blanks andthe like. In addition, a counter 32 associated with the packer 7 willgenerate a signal indicating the number of revenue stamps or coupons 19used by this same machine 7.

A sensor 8 a associated with the cigarette buffer 8 serves to generate asignal indicating the number of cigarettes 6 occupying the buffer.

The counters 20, 21, 22, 23, 24, 25 and 32 and the sensors 8 a, 26, 27,28, 29, 30 and 31 are connected on the output side to a master controlunit 33 which in turn is connected in conventional manner, notillustrated, to the internal control units of the single machines makingup the system 1.

The connections between the single counters and sensors and the controlunit 33 are not illustrated in FIG. 1.

The master control unit 33 is able to store and process data receivedfrom the counters and sensors.

Also connected to the master control unit 33 are a terminal device 34 byway of which to preset a nominal target number P_(n) of products, forexample boxes 15, to be turned out by the system 1 during a givenproduction run, and a terminal device 35 by way of which to preset aconstant factor C_(max) indicating the maximum output capacity of thesystem 1, that is to say its maximum capability, in terms of the maximumquantity of products in process that the system can accommodate.

Factor C_(max) is a number that will be dependent on the type ofmachines making up the system, and in particular their capacity to storefinished products or products in process temporarily, on the length andcapacity of the conveyors used in the system, and on the maximumcapacity of buffers or other inline storage facilities installed. Thevalue of C_(max) can be expressed as a number of cigarettes, that is tosay elementary products, or alternatively, according to respectiveconversion factors that will be constant and predetermined for eachbrand of products, as a number of packets, cartons or boxes. Forwhatever system and for any given brand of products, at all events,factor C_(max) remains a constant.

The method of managing the system 1 according to the present inventioninvolves counting the number P of at least one among the aforementionedproducts turned out by one of the machines. In particular, the number Pof boxes 15 turned out by the parceller 14 is monitored by the relativecounter 25, which relays a corresponding signal to the master controlunit 33.

At a given moment t₁ when the number of products P equals a referencevalue P_(r) such that the master control unit 33 recognizes a matchbetween the aforementioned target number P_(n) of boxes 15 and the sumof the number P_(r) of boxes 15 already packaged plus the value C_(max)indicating the maximum number of boxes 15 the system 1 is able toproduce, in other words when P_(n)=P_(r)+C_(max), the master controlunit 33 runs a first flash check on the actual quantity C₁ of products15 turned out by the system 1.

The flash check run by the master control unit 33 consists in comparingthe value of quantity C₁ registering at moment t₁ with theaforementioned constant factor C_(max), so it can establish what actionneeds to be applied to the system 1 on the basis of the comparison. Theprocedure in question will now be described with reference to FIG. 2.

Referring to the block diagram of FIG. 2, the master control unit 33will execute the following sequence of steps, of which the first step,or start, is indicated by a block denoted 36.

The start block 36 is followed by a block 37 that indicates both thestep of presetting the target number P_(n) of boxes 15 by way of thedevice denoted 34 in FIG. 1, and the step of presetting a value C_(max)representative of the maximum quantity of boxes 15 the system is able toproduce, by way of the device denoted 35 in FIG. 1.

The presetting block 37 is a followed by a block 38 that indicates thestep of counting the number P of products turned out by the singlemachines 3, 5, 7, 10, 12 and 14, and in particular, to reiterate, thenumber of boxes 15 turned out by the parceller 14, the last machine ofthe line 2.

The counting block 38 is followed by a comparison block 39 thatindicates the step of verifying a condition of parity between the numberP and the value P_(n)=P_(r)+C_(max). It will be observed that, likeP_(n) and C_(max), P_(r) is also a predetermined constant. At the momentt₁ when P matches P_(r) and the condition P_(n)=P_(r)+C_(max) issatisfied, a control signal will be relayed from the comparison block 39by way of the YES route to a successive monitoring block 40 which is inreceipt of input signals from the counters 20, 21, 22, 23, 24, 25 and 32and the sensors 8a, 26, 27, 28, 29, 30 and 31, of which the outputs areconnected to the master control unit 33, and capable of running thefirst flash check on the basis of the input data to verify the actualquantity C₁ of boxes 15 turned out by the system 1 at the predeterminedmoment t₁.

It will be observed that a signal returned via the NO route from thecomparison block 39 indicates that no control response is triggered,deferring the flash check as long as value P remains less than P_(r).

On receiving the control signal from the comparison block 39, themonitoring block 40 relays a signal indicating the actual quantity C₁ ofproducts to a second comparison block 41, which compares this quantityC₁ with the preset quantity C_(max) so it can establish what actionneeds to be applied to the system 1 on the basis of the comparison.

In the event that the value C₁ registering at moment t_(i) issubstantially the same as value C_(max), a signal is relayed via the YESroute to a block denoted 42, instructing preparation and initiation ofthe procedure for changeover to another brand of tobacco products. Theprocedure in question may be confined to a single machine, the cigarettemaker 3 for example, and concerned in particular with the operation ofemptying this same machine, or it might also cover the other machines ofthe system 1.

In the event that the value C₁ registering at moment t₁ is less than thevalue C_(max), no signal is relayed to the changeover block 42, whereasa signal is returned via a NO route to an event generator block denoted43 located externally of the master control unit 33, indicating thedifference between value C_(max) and value C₁ measured at moment t₁.

Assuming the difference in question corresponds to a given number ofcartons 15, say X, then at the moment t₂ when the counter 25 associatedwith the outfeed of the parceller 14 gives a tally of boxes 15corresponding to P_(r)+X, the event generator block 43 will relay acontrol signal to a further monitoring block 44 instructing a secondflash check of the actual quantity C₂ of boxes 15 turned out by thesystem 1 at the second moment t₂. On receiving the signal from the eventgenerator block 43, the monitoring block 43 relays a signal indicatingthe actual quantity C₂ of products to a further comparator block 45,which proceeds to compare this value C₂ with the previous value C₁.

Should it emerge from this comparison that C₂ is equal to C₁, a signalis relayed by the comparator block 45 via the YES route to thechangeover block 42, instructing preparation and initiation of theprocedure for the switch to another brand of products. Conversely, if C₂is less than C₁, a signal is returned by the comparator block 45 to theevent generator block 43, via the NO route, indicating the difference X′between value C₁ and value C₂.

At the moment t₃ when the counter 25 associated with the outfeed of theparceller 14 gives a tally of boxes 15 corresponding to P_(r)+X+X′, theevent generator 43 will relay a control signal to the monitoring block44 instructing a third flash check of the actual quantity C₃ of boxes 15turned out by the system 1 at the third moment t₃.

The steps of the method are repeated, and the flash checks will continueuntil the comparison produces a match expressed as C_(i)=C_(i-1), wherei=2, 3 . . . , which signifies that the target number P_(n) has beenreached.

It will be appreciated that in order to avoid overproduction, C_(i) mustnever be greater than C_(i-1). This can be ensured simply by pilotingthe system 1 to respond, with effect from the first flash check, byemptying the buffer 8 at least in part, and more generally by depletingall reserves of materials at the various machines, during the intervalbetween generic moments t_(i) and t_(i-1).

Similarly, it will be noted that the method of management describedabove uses a non-programmed, event-controlled type of loop where thesingle events are the consequence of measuring output numbers Pequivalent respectively, starting from the first event, to P_(r),P_(r)+X, P_(r)+X+X′, etc.

It has been found by experiment that the procedure can be concluded witha minimal number of flash checks, for example two or three.

The objects stated at the outset are thus realized with the methoddescribed above, in that consumable materials can be organized so as tominimize waste and avoid damage, and overproduction reduced to minimallevels, by virtue of a logic that is simple to implement and can be runautomatically by a monitoring, processing and control system using alimited number of sensing and computing operations.

In a variation on the method described above, illustrated in particularby the block diagram of FIG. 3, the single events are dictated by thevalue of output numbers P which, starting from the first event, will becompared with thresholds expressed respectively as P_(r), P_(r)+1,P_(r)+2, etc. In other words, the production threshold that determinesthe first event corresponds to P_(r)=P_(n)−C_(max) and each thresholddetermining a successive event is obtained by applying a unitaryincrement of the previous threshold.

In accordance with the principle already mentioned, the flash checksoccur at moments t₁, t₂, t₃ . . . that are not programmed, but ratherdependent on the production thresholds of one of the products turned outby one of the machines 3, 5, 7, 10, 12 and 14 making up the system 1. Itmight be advantageous, for example, to monitor the cigarette maker 3 andconsider the unitary increment in output from the machine as a furthernumber of cigarettes equivalent to the contents of one box 15.

To this end, the unitary increments in output from the cigarette maker 3will be constants typical of the brand in production.

Likewise in this instance it has been found by experiment that theprocedure can be concluded with a minimal number of flash checks, forexample two or three.

The block diagram of FIG. 3 differs from the block diagram of FIG. 2essentially in that the event generator denoted 43 is replaced by adifferent event generator denoted 46, again separate from the mastercontrol unit 33.

As illustrated in FIG. 3 and described previously with reference to FIG.2, as soon as P equals P_(r), the monitoring block 40 will receive acontrol signal from the first comparator block 39 and direct a signalindicating the actual quantity C₁ of products to the second comparatorblock 41, which in turn measures this value C₁ against the preset valueC_(max) indicating the maximum capacity of the system so as to establishwhat action needs to be applied on the basis of the comparison.

In the event that the value C₁ registering at moment t₁ is substantiallythe same as value C_(max), a signal will be relayed via the YES route tothe changeover block 42 instructing preparation and initiation of theprocedure for a switch to another brand of tobacco products.

In the event that the value C₁ registering at moment t₁ is less than thevalue C_(max), no signal is relayed to the changeover block 42, whereasa signal will be returned via a NO route to the event generator block 46enabling the generation of events subsequent to the first.

At the moment t₂ when the counter 20 associated with the cigarette maker3 registers an incremental number of cigarettes 4 equivalent to thecontents of one box 15, hence P=P_(r)+1, the event generator block 46relays a control signal to the monitoring block 44 ordering a secondflash check of the actual quantity C₂ of boxes turned out by the system1 at the second moment t₂.

The signal corresponding to value C₂ is sent to a comparator block 47which measures this same value C₂ against a value indicating thedifference between P_(n) and the number P=P_(r)+1 of boxes turned out upto moment t₂.

If the values match, a signal will be relayed by the comparator block 47via the YES route to -the changeover block 42 instructing preparationand initiation of the procedure for a switch to another brand of tobaccoproducts. If not, then a signal will be returned by the comparator block47 to the event generator block 46, via the NO route, enabling thegeneration of events subsequent to the second.

The steps of the method are repeated until the comparisons produce amatch expressed as P_(n)−P=C_(i), where i=2, 3 . . . .

It will be seen that the moments t₁, t₂, t₃ . . . at which flash checksare run could also be dependent on the consumption thresholds for anyone of the wrapping materials 18 or any one of the additional and/orauxiliary materials 19, for example the revenue stamps.

In all of the cases illustrated by way of example, moreover, the methoddisclosed could include the further step of establishing productionthresholds for at least one of the products turned out by a givenmachine 3, 5, 7, 10, 12 or 14 operating in the system on the basis of acorrection factor determined by statistical and/or experimental events.The step of defining a production threshold on the basis of a correctionfactor will take place following the last of a plurality of successiveflash checks to measure the actual quantities of products turned out bythe system 1.

1) A method of managing a system for the manufacture of tobacco productscomprising a plurality of machines, typically cigarette makers,cigarette packers, cartoners, cellophaners, parcellers and the like,turning out products consisting respectively in cigarettes, packets,cartons, overwrapped packets or cartons, and packs or boxes, wherein themachines of the system can be supplied respectively with wrappingmaterials consisting typically in paper, metal foil, polypropylene andlike, also with additional and/or auxiliary materials consistingtypically in revenue stamps, coupons and the like, characterized in thatit includes at least the steps of: programming a number (P_(n)) into amaster control unit, representing a nominal production target for atleast one predetermined product among those turned out by the machinesof the system; programming a value (C_(max)) into the master controlunit, representing the maximum output capacity of the system expressedas a quantity of the predetermined product; counting the number (P) ofat least one of the products emerging from the relative machine of thesystem and relaying a corresponding item of data to the master controlunit; running a first check on the actual quantity (C₁) of thepredetermined product turned out by the system, at a moment (t₁) whenthe number (P) of emerging products equals a value (P_(r)) such as willresult in a match (P_(n)=P_(r)+C_(max)) between the nominal productiontarget (P_(n)) for the predetermined product and the sum of the number(P_(r)) of products turned out plus the value (C_(max)) indicating themaximum output capacity of the system, the actual quantity (C1)expressing the real number of products in the making in the system suchnumber indicating the actual quantity (C1) being obtained by controllingand/or counting one or more countable parameters necessary for carryingout the tobacco manufacturing; comparing the value of the actualquantity (C₁) registering at the first check with the value (C_(max))indicating the maximum output capacity of the system, in order toestablish what action should be applied to the system on the basis ofthe comparison. 2) A method as in claim 1, comprising the further stepof initiating a procedure for changeover to another brand of tobaccoproducts in the event that the actual quantity (C₁) of productsregistering at the moment of the first check is substantially equal tothe value (C_(max)) indicating the maximum output capacity of thesystem. 3) A method as in claim 1, comprising the further step ofrunning at least a second check on the actual quantity (C₂, C₃ . . . )of the predetermined product turned out, in the event that the value ofthe actual quantity (C₁) of products registering at the moment of thefirst check is less than the value (C_(max)) indicating the maximumoutput capacity of the system. 4) A method as in claim 3, wherein thesecond check on the actual quantity (C₂) of the predetermined productturned out is run at a moment (t₂) established according to thedifference between the value (C_(max)) indicating the maximum outputcapacity of the system and the value of the quantity (C₁) measured atthe moment (t₁) of the first check. 5) A method as in claim 4,comprising the further steps of running a plurality of checks subsequentto the second check on the actual quantity (C₃, C₄ . . . ) of thepredetermined product turned out, wherein each check from the secondonwards will determine the moment of running the next check, accordingto the difference between the value (C_(i-1)) corresponding to theoutput quantity measured at the previous check and the value (C_(i))corresponding to the quantity measured at the current moment. 6) Amethod as in claim 5, wherein the moments at which the checks are rundepend on respective production thresholds programmed for one of theproducts turned out by a given machine of the system. 7) A method as inclaim 6, wherein the production thresholds are referable to any one ofthe machines making up the system, and each threshold comprises a numberof relative products equal to or constituting a multiple of the numberof products constituting the end product. 8) A method as in claim 6,wherein the production thresholds are referable to the final machine ofthe system. 9) A method as in claim 8, wherein the procedure forchanging over to another brand of tobacco product is initiated when,following the steps of running a plurality of successive checks onoutput quantities (C₂, . . . C_(i), . . . ) subsequent to the quantity(C₁) measured at the moment (t₁) of the first check, there is a match(P_(n)−P=C_(i)) between a value given by the production target (P_(n))for at least one predetermined product among the products turned out bythe machines less the number (P) of at least one of the products turnedout by the corresponding machine of the system, and the value of thequantity (C₁) measured at a corresponding moment (t_(i)) of running thecheck. 10) A method as in claim 9, wherein the moments (t₁, t₂, . . .t_(i)) of running the checks are dependent on the consumption thresholdsfor at least one of the wrapping materials or the addition and/orauxiliary materials used by at least one predetermined machine of thesystem. 11) A method as in claim 8, comprising the further step ofestablishing the production thresholds for at least one of the products,turned out by a given machine of the system, on the basis of acorrection factor determined by statistical and/or experimental events.12) A method as in claim 11, wherein the step of establishing theproduction threshold on the basis of a correction factor takes placefollowing the last of a plurality of successive checks to measure theactual quantities of products turned out. 13) A method as in claim 1,wherein the moments at which the checks are run depend on respectiveproduction thresholds programmed for one of the products turned out by agiven machine of the system. 14) A method as in claim 3, wherein theprocedure for changing over to another brand of tobacco product isinitiated when, following the steps of running a plurality of successivechecks on output quantities (C₂, . . . C_(i), . . . ) subsequent to thequantity (C₁) measured at the moment (t₁) of the first check, there is amatch (P_(n)−P=C_(i)) between a value given by the production target(P_(n)) for at least one predetermined product among the products turnedout by the machines less the number (P) of at least one of the productsturned out by the corresponding machine of the system, and the value ofthe quantity (C₁) measured at a corresponding moment (t_(i)) of runningthe check. 15) A method as in claim 1, wherein the moments (t₁, t₂, . .. t_(i)) of running the checks are dependent on the consumptionthresholds for at least one of the wrapping materials or the additionand/or auxiliary materials used by at least one predetermined machine ofthe system. 16) A method as in claim 6, comprising the further step ofestablishing the production thresholds for at least one of the products,turned out by a given machine of the system, on the basis of acorrection factor determined by statistical and/or experimental events.17) A method as in claim 2, wherein the moments at which the checks arerun depend on respective production thresholds programmed for one of theproducts turned out by a given machine of the system. 18) A method as inclaim 3, wherein the moments at which the checks are run depend onrespective production thresholds programmed for one of the productsturned out by a given machine of the system. 19) A method as in claim 4,wherein the moments at which the checks are run depend on respectiveproduction thresholds programmed for one of the products turned out by agiven machine of the system. 20) A method as in claim 4, wherein theprocedure for changing over to another brand of tobacco product isinitiated when, following the steps of running a plurality of successivechecks on output quantities (C_(2,) . . . C_(i), . . . ) subsequent tothe quantity (C₁) measured at the moment (t₁) of the first check, thereis a match (P_(n)−P=C_(i)) between a value given by the productiontarget (P_(n)) for at least one predetermined product among the productsturned out by the machines less the number (P) of at least one of theproducts turned out by the corresponding machine of the system, and thevalue of the quantity (C₁) measured at a corresponding moment (t_(i)) ofrunning the check.